An Introduction to Laser Technology and Its Applications
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2018–2019 SCIENCEResource Guide Northwest Pa. Collegiate Academy - Erie, PA An Introduction to Laser Technology and Its Applications The vision of the United States Academic Decathlon® is to provide all students the opportunity to excel academically through team competition. Toll Free: 866-511-USAD (8723) • Direct: 712-326-9589 • Fax: 651-389-9144 • Email: [email protected] • Website: www.usad.org This material may not be reproduced or transmitted, in whole or in part, by any means, including but not limited to photocopy, print, electronic, or internet display (public or private sites) or downloading, without prior written permission from USAD. Violators may be prosecuted. Copyright ® 2018 by United States Academic Decathlon®. All rights reserved. Table of Contents INTRODUCTION . .4 Rainbows . .21 Total Internal Reflection ...................22 SECTION I: LIGHT . .5 Fiber-Optics . .23 Introduction . 5 Mirrors and Lenses ....................23 Properties of Light . 5 Plane Mirrors............................23 Concave and Convex Mirrors . .25 Waves . 5 Concave Mirrors . .25 Wave Properties . 5 Convex Mirrors . .26 Electromagnetic Waves ....................6 Lenses..................................27 The Speed of Light . 8 Converging Lenses.....................28 The Electromagnetic Spectrum...............9 Diverging Lenses . .29 Antennas and Radio Waves................10 Spherical and Chromatic Aberration ......29 Transparent vs. Opaque Materials . 11 Wave Optics .........................30 Visible Light and Color . 12 Huygens’ Principle .......................30 The Visible Spectrum......................12 Diffraction . .30 Selective Absorption and Reflection . .13 Interference .............................31 Selective Transmission . .14 Superposition .........................31 Blue Skies and Red Sunsets . .14 Double Slit Interference.................32 Section I Summary ....................16 Diffraction Gratings ....................34 Thin-Film Interference . .34 Northwest Pa. Collegiate Academy - Erie, PA SECTION II: OPTICS . 17 Polarization .............................35 Introduction . 17 Optical Instruments ....................37 Geometric Optics . 17 Simple Magnifier . .37 Microscopes . .37 The Ray Approximation ...................17 Telescopes..............................38 Reflection...............................17 The Law of Reflection...................17 Section II Summary....................39 Specular and Diffuse Reflection . .18 Refraction...............................18 SECTION III: LASERS..............41 The Law of Refraction . .19 Introduction . 41 Mirages . .20 Dispersion . .21 Light Emission and Absorption ...........41 2018–2019 Science2 Resource Guide The Atom . 41 Scientific Applications..................67 Quantization ............................42 Laser Spectroscopy.......................67 Photons . .42 Confocal Laser Scanning Microscopy .......67 The Bohr Model . .44 Manipulating Tiny Objects.................68 Atomic Excitation and Emission . .45 Optical Tweezers ......................68 Emission Spectra .........................47 Laser Cooling .........................70 Incandescence . .48 Atomic Clocks . .71 Absorption Spectra.......................50 Nuclear Fusion . .71 Fluorescence . .51 Phosphorescence . .52 Medical Applications . 73 Lamps..................................53 Laser Surgery ...........................73 Incandescent Lamps....................53 Refractive Eye Surgery . .75 Fluorescent Lamps and CFLs .............53 Laser Dermatology .......................76 Light-Emitting Diodes ...................54 Laser Dentistry...........................77 Lasers ...............................55 Industrial Applications . 78 Laser Operation . .55 Laser Drilling . .78 Stimulated Emission . .56 Laser Cutting . .78 Population Inversion....................57 Laser Beam Welding......................79 Energy Levels . .58 Laser Marking, Engraving, and Etching . .79 Optical Cavity . .59 Photolithography.........................80 Properties of Laser Light . .59 Stereolithography ........................80 Monochromatic .......................60 Other Applications ....................81 Directional ...........................60 Barcode Readers . 81 Coherent.............................60 Laser Pointers............................81 Types of Lasers . .60 Laser Printers . .82 Gas Lasers ...........................60 Optical Discs: CDs, DVDs, and Others .......83 Solid-State Lasers . 61 Holography.............................84 Semiconductor Diode Lasers.............62 Section IV Summary . 86 History of the Laser ....................62 Northwest Pa. Collegiate Academy - Erie, PA 1900–50: Early Foundations . .62 CONCLUSION ...................87 Early 1950s: Charles Townes and the Maser...........................63 TIMELINE .......................88 Late 1950s: Laser Conceived...............63 1960s: The Race to Build the Laser . .64 GLOSSARY......................90 1970s–Present . .64 Section III Summary . 65 NOTES . .94 BIBLIOGRAPHY . .95 SECTION IV: APPLICATIONS OF LASERS . .67 Introduction . 67 2018–2019 Science3 Resource Guide Introduction The laser is among the most important inventions of the the phenomena of reflection, refraction, and diffraction. As twentieth century. Since its introduction in 1960, the we will see, lenses and mirrors can be configured to focus laser has made possible a countless number of scientific, light in particular ways, which will become important in medical, industrial, and commercial applications. Theodore understanding laser operation and applications. Maiman, the inventor of the first working laser, was quoted by The New York Times in 1964 as calling the laser “a Section III will provide an overview of the laser itself. solution seeking a problem.” Today it’s nearly impossible We will start by considering how light emission can be to go an entire day without using at least one object that explained using a quantum model of atomic excitation, and was either manufactured using lasers or that uses lasers in explore various mechanisms of light emission. By the end order to function. In this Science Resource Guide, we will of this section, you will be familiar with the most important explore the nature of light and optics, the basic operation properties of laser light, the main categories of lasers, and of a laser, and the various applications of lasers that have the history behind the development of the laser. transformed our lives over the course of more than half Finally, Section IV will provide an overview of major a century. Along the way, we will consider significant applications of lasers across several categories. Lasers are milestones in the development of the laser, as well as the an important tool in a variety of research fields, and they people who contributed to our understanding of both lasers have also made possible new surgical procedures and and light itself. You’ll also have opportunities to explore manufacturing techniques. Lasers are all around us, in laser light-related phenomena using online simulations and pointers, laser printers, and optical disc readers. By the end simple demonstrations with everyday materials. of this guide, you will be able to explain how lasers work Section I will cover the basic properties of light as an and the significant ways in which they contribute to our electromagnetic wave. In this section, we will discuss how daily lives. visible light represents a relatively small segment of the complete electromagnetic spectrum. We will also explore how the colors that we see are caused by interactions NOTE TO STUDENTS: You will notice as you read through between visible light and matter. the Resource Guide that some key terms and phrases are Northwest Pa. Collegiate Academy - Erie, PA boldfaced. These terms are included in the glossary at the In Section II, we will consider the field of optics, which end of the Resource Guide. concerns the behavior of light, the formation of images, and 2018–2019 Science4 Resource Guide Section I Light INTRODUCTION disturbs the water further out, which disturbs the water further out, and so on (FIGURE 1). Light is both a familiar and fascinating phenomenon. Although a laser beam and a flashlight beam have very Waves can be classified as transverse or longitudinal. A different properties, they are still governed by the same transverse wave is made up of oscillations that are fundamental principles that describe light. In this section, perpendicular to the direction that the wave travels. As we will set the stage for our discussion of the laser by we will see, light is an example of a transverse wave. In covering some of the most fundamental properties of light contrast, for a longitudinal wave, the oscillations are and color. parallel to the direction that the wave travels. Sound is an example of a longitudinal wave. Regardless of their classification, all waves are caused by a vibration of some PROPERTIES OF LIGHT kind. For example, sound waves originate from vibrations of matter, such as a person’s vocal chords or a guitar WAVES string, which initiate a sequence of collisions between air Many phenomena in the known universe are described by molecules that eventually reaches your eardrum. the general mathematical concept of waves. For example, the beam of light produced by a laser, the sound generated Waves transport energy but not mass. That is, waves do not by a thunderclap, and the ripples of water in a pond are carry matter along with them from one point to another as all waves.